Diffractive neutrino production of pions on nuclei: Adler relation within the color-dipole description

Abstract

Effects of coherence in neutrino production of pions off nuclei are studied employing the color-dipole representation and path integral technique. If the nucleus remains intact, the process is controlled by the interplay of two length scales. One is related to the pion mass and is quite long (at low Q 2 ), while the other, associated with heavy axial-vector states, is much shorter. The Adler relation is found to be broken at all energies, but especially strongly at * 10 GeV, where the cross section is suppressed by a factor $A À1=3 . On the contrary, in a process where the recoil nucleus breaks up into fragments, the Adler relation turns out to be strongly broken at low energies, where the cross section is enhanced by a factor $A 1=3 , but has a reasonable accuracy at higher energies, where all the coherence length scales become long.

Photon emission in neutral-current interactions at intermediate energies

“…Incoherent pion production has also been scrutinized using microscopic models for the reaction mechanism on the nucleon [34][35][36][37][38][39], with special attention paid to pion final state interactions in nuclei [39][40][41][42][43]. New microscopic models have been developed for coherent pion production [44][45][46][47][48] while traditional ones, based on the partial conservation of the axial current (PCAC), have been updated [49][50][51][52].…”

Simultaneous measurement of muon neutrino $ν_μ$ charged-current single $π^+$ production in CH, C, H$_2$O, Fe, and Pb targets in MINERvA

“…Coherent pion production is reweighted in both the energy of the pion E π and θ π to agree with a recent measurement of coherent pion production in the medium energy NuMI beam [35]. Additionally, the normalization of coherent pion production is increased by 43.7% in order to account for coherent interactions on hydrogen known as diffractive pion production, based on the Kopeliovic model [36].…”

Measurement of neutrino-induced neutral-current coherent π0 production in the NOvA near detector

“…Alternatively, the DFR cross section can be estimated by a similar method as in Ref. [47] from the calculation of inclusive νp → νpπ 0 by Kopeliovich et al, which is based upon the PCAC hypothesis and includes both DFR and non-DFR contributions [37,38]. In Fig.…”

“…However, the Rein model is valid only for the hadronic invariant mass W > 2 GeV region, which is too high for the energy range of NOvA. To simulate the DFR background for this measurement, events are first generated by the Rein model in GENIE (v2.12.2) and then reweighted to an estimation based upon the PCAC calculation by Kopeliovich et al, which includes both DFR and non-DFR contributions [37,38]. In this estimation, Kopeliovich's prediction of dσ dðjtj−jtj min Þ for inclusive νp → νpπ 0 is fitted with GENIE (without DFR) and an exponential term, where jtj min is the minimum possible value of jtj.…”